1. Field of the Invention
The present invention relates to a photoelectric conversion device having a semiconductor junction and a method for manufacturing the photoelectric conversion device.
2. Description of the Related Art
In response to global environmental issues in recent years, the market for photoelectric conversion devices typified by solar cells such as residential photovoltaic systems has expanded. Bulk photoelectric conversion devices which are formed using single crystal silicon or polycrystalline silicon with high photoelectric conversion efficiency have already been put into practical use. The photoelectric conversion devices using single crystal silicon or polycrystalline silicon are manufactured by being cut out of large silicon ingots. However, it takes a long time to manufacture large silicon ingots, which means productivity is low, and since supply of raw materials of silicon itself is limited, the supply of silicon ingots is insufficient and cannot respond to the expansion of the market.
While shortage of silicon materials is obvious as described above, thin film photoelectric conversion devices formed using amorphous silicon thin films and microcrystalline silicon thin films has attracted attentions. In thin film photoelectric conversion devices, silicon thin films are formed over supporting substrates by a variety of chemical or physical vapor deposition methods. Therefore, it is said that thin film photoelectric conversion devices can save resources and can achieve low cost as compared to bulk photoelectric conversion devices.
In addition, a photoelectric conversion device formed using a microcrystalline silicon thin film which can be manufactured by a plasma CVD method is developed (for example, see Patent Document 1: Japanese Published Patent Application No. 2000-277439).
As a crystal-system silicon film formed by a plasma CVD method and a photoelectric conversion device using the crystal-system silicon film, a photoelectric conversion device using a semi-amorphous semiconductor are reported (for example, refer to References 2 and 3: Japanese Examined Patent Application Publication No. H2-53941 and Japanese Examined Patent Application Publication No, S62-62073). The semi-amorphous semiconductor has a semi-amorphous or semi-crystalline structure, which is different from an amorphous semiconductor or a crystalline semiconductor.